New to Finishing

Hello and this is my forst post. I am looking for some help in finishing black furniture with a semi gloss final coat. Lots of questions however first,

Sanding betwee coats. I am preping the piece as best as posible. First applying a base coat, alowing it to dry and cure over night. How much sanding is required before I apply a coat of black? Is sanding really necessary? Than the final coat of laquer. So how much sanding is really needed between coats?

By the way, I am in South America, close to the equator, humidity is high. I have a home made booth, about 8×10, an intake fan and an exhaust fan.

Any advice is welcomed…...

Thanks, Martin

4 replies so far

Are you using water base paint? If so, the first coat will raise the grain and you will have to knock that back w/ 320 or 400 grit. If you start w/ a de-waxed shellac sealer you can avoid that. Then you may not need to sand at all between coats. It just depends on how it feels, if it is rough between coats then sand.

I am using an oil base primer made for cars, thick and grey in color, mixing it with black tint, thinner and a fine grey powder they call taulk, then spraying it with a gun. The furniture is a mix of MDF where I have a lot of flat surface and oak where I need structial strength.

Tomorrow I am going to try an experiment on a dresser that is mostly flat MDF. Spray the base, wait untill it sets, spray the color (black), agian wait untill it sets and then spray the finnish.

I am a long way from an expert in the finishing arena, using mostly Danish oil and Polyurethane. However, I have some thoughts:

1) When you are doing your experiment, add a scrap of oak to the MDF. The pores in the oak will probably result in a distinctly different appearance from the MDF.

2) From what I have gathered about sanding during the finishing process, there are 3 purposes. A) Achieve a smooth to the touch feel of the final coat. B) Improved adhesion of the next coat, probably more important when changing from one type of finish to another. C) Enhance the sheen by sanding with really fine paper.

3) I generally raise the grain of wood by dampening it with water before the final sanding of the raw wood. I have painted MDF with water borne paint and the finish coat was smooth with no sanding. Therefore dampening the MDF is probably unnecessary and may be harmful.

4) When I apply polyurethane, I usually sand after the first coat. After the first coat the wood feels rough to the touch. This is probably due to minute amounts of dust remaining on the wood. I get better results when I do a thorough job of tacking the wood before the first coat.

5) I rarely sand the finish after the first coat and its sanding. But then I am using polyurethane, which ends up smooth to the touch and imparts the desired level of shine.

6) When I do sand the finish, I sand until the finish is dull and quit before the sanding through the finish. I check that it is enough sanding by vacuuming the dust from the surface and look at the sheen (should be dull) and run my hand over it to ensure it is smooth.

7) Steel wool can lead the finishing problems down the road. If all the stray metal fibers are not removed, these can rust and discolor the finish.

8) Lastly, were I to change the varnish from what I normally use, I would do exactly what you are doing. With pieces of scrap from which the project was made, take them through the entire finishing process. I would rather discover problems on scrap than have to fix a problem on the project.